782 



After the completion of these experiments with Phycomyces I hope 

 to study the behaviour of the stem and the root in higher plants. 



After tiie phenomenon described above had been established qua- 

 litativel}', I was naturally cui-ions as to how far this photo-growth- 

 reaction was related to the well-known phototropism of Phycomyces. 

 In order to investigate this, the plant was illnminated unilaterally 

 with, for example, 14 metre candle power during 60 sec. and at 

 the same time the growth and the occurrence of a curvature were 

 watched tiirough a telescope. 



It was then found that — excluding the special case, which is 

 described below — a positive curvature never appears, unless the 

 above-described acceleration of groivth has previously taken place. The 

 positive photo-growth-reaction occurs in the usual manner after 

 about 3 min. — this time of reaction can with the weakest illumi- 

 nations rise to 7 min. — it reaches its maximum, then the rate ot 

 growth diminishes again, and from this moment does the positive 

 phototropic curvature become visible, which, according to the con- 

 ditions of illumination becomes more or less strong. A few examples 

 are given in tables IV and V. 



